Objective:
(1) To develop and characterize hybrids using normal and waxy GEM lines to produce hybrids with improved starch-ethanol conversion efficiency and to increase ethanol yield.
(2) To develop healthy foods (high-amylose popcorn) and healthy food ingredients (slowly digestible starch) using GEM lines. In previous studies we found that waxy corn had substantially greater starch-ethanol conversion efficiency (93.0%, average of 8 lines) than normal corn (88.2%, average of 4 lines). The starch content of waxy corn (average 68.3%), however, was less than that of the normal corn (average 71.9%), and no information was collected for yield in the field. Consequently, the lab results indicated that ethanol yield of dry-grind waxy corn (36g/100g corn) was approximately the same as that produced using the normal corn. A preliminary study has shown that crosses of a waxy corn line with a normal corn line results in hybrids with improved enzyme digestibility. Because enzyme digestibility of starch is positively correlated with starch-ethanol conversion efficiency, it suggested that hybrids made by crossing waxy × normal had promising potential to increase the yield of ethanol. We plan to continue the study to determine if hybrids made by crossing waxy × normal GEM lines can improve the yield of ethanol in the field and to evaluate the dosage effects of the waxy gene on ethanol production in the harvested grain. For our second objective, we plan to further study the feasibility of producing popcorn with improved nutritional and health value by using high amylose germplasm. Our preliminary results have shown that crosses made with a high amylose GEM line crossed to several popcorn inbreds had reasonable popping potential and slower enzyme-digestibility. We plan to continue the study to improve the popping rate while maintaining the slow digestibility of starch to reduce the glycemic index and develop healthy popcorn products. Slowly-digestible and resistant starch were also developed by crossing GEM lines that consist of high lipid-contents and high amylose-contents. Preliminary analysis had shown reduction in enzyme digestibility of the starch produced for crosses made between high-amylose corn lines × high-oil corn lines. We'll characterize the high-amylose/high-oil cornstarch to understand its structure and properties and the mechanism of its enzyme digestibility.

Approach:
Objective 1. GEM materials to be used in this study include three isogenic lines of waxy GEM releases: GEMS-0185, GEMN-0186, GEMS-0206, and in addition their three corresponding normal (non-waxy) counterparts. Two F1 waxy hybrids (GEMS-0185 × GEMN-0186 and GEMS-0203 × GEMN-0186) and their normal counterparts will be studied which include six hybrids; waxy × waxy, waxy × normal, and normal × normal for each of the two F1 pedigrees. Yield trials will be planted at four locations, and in the GEM nursery and hand pollinated for starch analysis. The dosage effects of waxy gene will be studied using an enzymatic method for total-starch content. Starch will be isolated from kernels and physical properties analyzed which include gelatinization, retrogradation rate, swelling power of starch granules, pasting properties, and enzyme digestive rates. Dosage effects of waxy gene on the structure and properties of the starch will be determined. The hand pollinated grain (F2 generation seed) of waxy × waxy, waxy × normal, and normal × normal will be subjected for ethanol production studies in the lab to evaluate the dosage effect of waxy gene on ethanol yield.
Objective 2. High-amylose popcorn hybrids have been developed using GEMS-0067 × three popcorn public inbreds; GEMS-0067 × Sg1533, GEMS-0067 × Hp301, and GEMS-0067 × Hp72-11. Comparison will be made with B73 crossed to the same popcorn inbreds. Starch of the six hybrids will be isolated and subjected to structural analyses to determine the amylose content and amylopectin structure. The isolated starch will be analyzed for gelatinization properties and enzyme digestibility. The high-amylose popcorn will be subjected to popping tests to determine the effect of high amylose-content on the popping ability. After popping, the high-amylose popcorn will be sampled for sensory evaluations to find consumer acceptance of the product as a healthy alternative for traditional popcorn.
High-amylose × high-oil germplasm have been developed using two GEM lines; GEMN-0131, and a 50% tropical inbred derived from CUBA164:S15. The two lines were crossed to a high-amylose inbred line from Truman State University designated Truman 40. The hybrid corn will be analyzed for the starch, oil, and protein contents. Starch of the hybrid corn and the parent lines will be isolated and subjected to structural and property analyses. The amylose and lipid contents of the starch will be analyzed, and correlations between the lipid content of the starch and oil content of the kernels will be determined. Thermal properties of the starch, swelling power, and pasting properties of isolated starch will be determined and correlated with the lipid content. Enzyme digestibility of isolated starch and starch in dry-grind corn will be analyzed, and the effects of lipid contents on the starch digestibility will be evaluated.